Chapter 4 Review Packet Answer Section

MULTIPLE CHOICE

1. ANS: D PTS: 1 2. ANS: D PTS: 1 3. ANS: B PTS: 1 4. ANS: A PTS: 1 5. ANS: D PTS: 1 6. ANS: A PTS: 1 7. ANS: C PTS: 1 8. ANS: C PTS: 1 9. ANS: C PTS: 1 10. ANS: C PTS: 1 11. ANS: B PTS: 1 12. ANS: E PTS: 1 13. ANS: C PTS: 1 14. ANS: D PTS: 1 15. ANS: D PTS: 1 16. ANS: D PTS: 1 17. ANS: C PTS: 1 18. ANS: B PTS: 1 19. ANS: D PTS: 1 20. ANS: C PTS: 1

OTHER

1. ANS: (a) This is an experiment because treatments (aspirin and alcohol; alcohol only) are imposed on the subjects. (b) Explanatory variable: Aspirin consumption; Response: blood alcohol content. (c) Matched pairs experiment. Each subject was given both treatments (aspirin before drinking and no aspirin) and thus acted as his own “pair.” (d) Significantly means that the difference found in the subject’s blood alcohol level between the two treatments was large enough that it was unlikely to have arisen from chance variation. (e) Each subject acted as his or her own control, drinking alcohol alone and alcohol with aspirin. Comparing each subject’s blood alcohol under both treatments allowed the researchers to isolate the impact of aspirin from any other variables.

PTS: 1 2. ANS: (a) A randomized block design—blocking by gender—will reduce the impact that differences between the responses of men and women to the treatment might have on variability arising from random assignment. (b) A larger number of subjects—greater replication—decreases the impact of random variation on experimental results, thereby increasing our ability to distinguish the effects of the treatment. (c) First create two blocks comprised of the 70 women and the 56 men. Then, within each block assign the women numbers from 01 to 70 and the men numbers from 01 to 56. Choose 2-digit numbers from the random number table, ignoring repeats and unassigned numbers, until you have selected 35 women. Then begin elsewhere in the table and follow the same procedure to randomly select 28 men. These subjects will be given the new migraine treatment, and the remaining subjects will receive a commonly-used standard treatment. Compare relief from migraine pain between the treatment group and the control group.

PTS: 1 3. ANS: (a) Wording of question bias: it’s possible that using the phrase “government censorship of artistic expression” generates a positive response more often than a more neutral phrase, so that 85% is an overestimate of support. (b) Because the survey is only given to people over 50 who have paid to join AARP, the survey suffers from undercoverage of the young and those who do not have enough income to pay for membership in AARP. Thus the survey will probably underestimate support for the program. (There are other plausible answers, such as wording of the question or response bias).

PTS: 1 4. ANS: Question is flawed because it includes a position that leads a participant towards a certain response, introducing bias. Another plausible answer is that the question is biased because there are two positive choices and one (strongly) negative choice for answers.

PTS: 1 5. ANS: No, it introduces non-response bias. If the 13 students who didn’t respond all held similar opinions, adding 13 newly-selected students would not accurately represent the views of the original

PTS: 1 6. ANS: The method completely confounds gender with whatever the treatment is, since all the males are in one group and all the females are in the other. It will be impossible to separate the effect of the treatment from the effects due to gender.

PTS: 1 7. ANS: (a) Neither the subjects nor the researchers who administered the learning and memory tests knew which subjects were taking the gingko extract and which were taking the placebo. (b) Since subjects were randomly assigned to groups, we can make inferences about cause and effect. But because the subjects were volunteers and not randomly selected from the population (healthy people over 60), we cannot make inferences about the population as a whole. (c) A larger number of subjects—greater replication—decreases the impact of random variation on experimental results, thereby increasing our ability to distinguish the effects of the treatment. (d) “No statistical significance” means that the differences found in memory and concentration between subjects in the two treatments was small enough so that it could be attributable to variation between randomly- assigned subjects, rather than an effect of the treatment. (e) Assign the volunteers numbers from 001 to 230. Starting on line 103, choose 3-digit numbers from the table, ignoring unassigned numbers and repeats, until you have selected 115 numbers for the treatment group. By this method, the first five numbers are 170, 005, 227, 118, 007.

PTS: 1